Cost-effectiveness of currently recommended direct-acting antiviral treatments in patients infected with genotypes 1 or 4 hepatitis C virus in the US

OBJECTIVE

This study compared the cost-effectiveness of direct-acting antiviral therapies currently recommended for treating genotypes (GT) 1 and 4 chronic hepatitis C (CHC) patients in the US.

METHODS

A cost-effectiveness analysis of treatments for CHC from a US payer's perspective over a lifelong time horizon was performed. A Markov model based on the natural history of CHC was used for a population that included treatment-naïve and -experienced patients. Treatment alternatives considered for GT1 included ombitasvir/paritaprevir/ritonavir + dasabuvir ± ribavirin (3D ± R), sofosbuvir + ledipasvir (SOF/LDV), sofosbuvir + simeprevir (SOF + SMV), simeprevir + pegylated interferon/ribavirin (SMV + PR) and no treatment (NT). For GT4 treatments, ombitasvir/paritaprevir/ritonavir + ribavirin (2D + R), SOF/LDV and NT were compared. Transition probabilities, utilities and costs were obtained from published literature. Outcomes included rates of compensated cirrhosis (CC), decompensated cirrhosis (DCC), hepatocellular carcinoma (HCC) and liver-related death (LrD), total costs, life-years and quality-adjusted life-years (QALYs). Costs and QALYs were used to calculate incremental cost-effectiveness ratios.

RESULTS

In GT1 patients, 3D ± R and SOF-containing regimens have similar long-term outcomes; 3D ± R had the lowest lifetime risks of all liver disease outcomes: CC = 30.2%, DCC = 5.0 %, HCC = 6.8%, LT = 1.9% and LrD = 9.2%. In GT1 patients, 3D ± R had the lowest cost and the highest QALYs. As a result, 3D ± R dominated these treatment options. In GT4 patients, 2D + R had lower rates of liver morbidity and mortality, lower cost and more QALYs than SOF/LDV and NT.

LIMITATIONS

While the results are based on input values, which were obtained from a variety of heterogeneous sources-including clinical trials, the findings were robust across a plausible range of input values, as demonstrated in probabilistic sensitivity analyses.

CONCLUSIONS

Among currently recommended treatments for GT1 and GT4 in the US, 3D ± R (for GT1) and 2D + R (for GT4) have a favorable cost-effectiveness profile.

Cost-Effectiveness of Genotype 1 Chronic Hepatitis C Virus Treatments in Patients Coinfected with Human Immunodeficiency Virus in the United States

INTRODUCTION

New treatments for chronic hepatitis C virus (HCV) are highly effective in patients coinfected with human immunodeficiency virus (HIV). This study estimated the cost-effectiveness of treatments for genotype 1 (GT1) HCV in HIV-coinfected patients.

METHODS

A Markov model based on HCV natural history was used. The base-case analysis included both treatment-naïve and -experienced patients. Alternatives were ombitasvir/paritaprevir/ritonavir, dasabuvir with or without ribavirin (3D ± R) for 12 or 24 weeks, sofosbuvir plus peginterferon and R (SOF + PR) for 12 weeks, SOF + R for 24 weeks, and no treatment (NT). A subgroup analysis restricted to treatment-naïve, non-cirrhotic patients compared 3D ± R for 12 weeks to SOF plus ledipasvir (LDV) for 12 weeks and NT. Transition probabilities, utilities, and costs were obtained from the published literature. Outcomes were measured over a lifetime horizon and included rates of compensated cirrhosis, decompensated cirrhosis, hepatocellular carcinoma and liver-related death, total costs, life-years, quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio (ICER).

RESULTS

In the base-case, SOF + R was dominated by both SOF + PR and 3D ± R. Compared to SOF + PR, 3D ± R had an ICER of $45,581. The lifetime rates of liver morbidity and mortality were lower among those treated with 3D ± R compared to SOF + PR, SOF + R, or NT. In the subgroup analysis, 3D ± R was cost-effective compared to NT at a threshold of $50,000 per QALY (ICER $27,496). SOF/LDV had an ICER of $104,489 per QALY gained compared to 3D ± R.

CONCLUSION

In the GT1 HCV population coinfected with HIV, 3D ± R was cost-effective compared to NT, SOF + R, and SOF + PR. In the treatment-naïve sub-population, 3D ± R was cost-effective compared to NT and SOF/LDV.

Safety and Efficacy of Ombitasvir/Paritaprevir/Ritonavir Plus Dasabuvir With or Without Ribavirin in HCV-Infected Patients Taking Concomitant Acid-Reducing Agents

OBJECTIVES

Acid-reducing agents (ARAs) and proton-pump inhibitors (PPIs) that increase gastric pH can alter the bioavailability of antiviral drugs, particularly relevant in patients with advanced liver disease caused by chronic hepatitis C virus (HCV) infection seeking therapy. Using integrated data from six phase 3 studies, we report the safety and efficacy of the 3-direct-acting antiviral (DAA) regimen containing ombitasvir (OBV, an NS5A inhibitor), ritonavir-boosted paritaprevir (PTV/r, an NS3/4A protease inhibitor), and dasabuvir (DSV, an NS5B polymerase inhibitor) with or without ribavirin (RBV) for HCV genotype 1 patients taking concomitant ARAs and PPIs.

METHODS

Treatment-naïve or peginterferon/RBV treatment-experienced patients with or without compensated cirrhosis received OBV/PTV/r and DSV with or without weight-based RBV. Rates of sustained virologic response (SVR), defined as HCV RNA below the lower limit of quantification, 12 weeks post-treatment (SVR12) and safety were evaluated in patients who were receiving concomitant ARAs.

RESULTS

Among 2,053 patients enrolled and dosed with study drug, 410 (20%) were receiving concomitant ARAs; of these, 308 (15%) were taking concomitant PPIs. Rates of SVR12 were 95.9% (95% confidence interval (CI) 93.5-97.4%) among patients receiving an ARA, and 96.3% (95% CI 95.3-97.2%) in patients not receiving a concomitant ARA. Similarly, among patients receiving a PPI or not, SVR12 was achieved in 95.1% (95% CI 92.1-97.0%) and 96.4% (95% CI 95.5-97.2%), respectively. Response rates were high regardless of treatment regimen (with or without RBV), and among patients receiving a standard or high dose of PPIs. Regarding safety, adverse events and serious adverse events were more frequently reported in patients taking concomitant ARAs, though baseline population differences may have played a role.

CONCLUSIONS

In phase 3 trials of OBV/PTV/r plus DSV and RBV in HCV genotype 1-infected patients, SVR12 rates were high regardless of ARA/PPI use or PPI dose. These data support the co-administration of this regimen with ARAs including PPIs.

Economic and Public Health Impacts of Policies Restricting Access to Hepatitis C Treatment for Medicaid Patients

BACKGROUND

Interferon-free hepatitis C treatment regimens are effective but very costly. The cost-effectiveness, budget, and public health impacts of current Medicaid treatment policies restricting treatment to patients with advanced disease remain unknown.

OBJECTIVES

To evaluate the cost-effectiveness of current Medicaid policies restricting hepatitis C treatment to patients with advanced disease compared with a strategy providing unrestricted access to hepatitis C treatment, assess the budget and public health impact of each strategy, and estimate the feasibility and long-term effects of increased access to treatment for patients with hepatitis C.

METHODS

Using a Markov model, we compared two strategies for 45- to 55-year-old Medicaid beneficiaries: 1) Current Practice-only advanced disease is treated before Medicare eligibility and 2) Full Access-both early-stage and advanced disease are treated before Medicare eligibility. Patients could develop progressive fibrosis, cirrhosis, or hepatocellular carcinoma, undergo transplantation, or die each year. Morbidity was reduced after successful treatment. We calculated the incremental cost-effectiveness ratio and compared the costs and public health effects of each strategy from the perspective of Medicare alone as well as the Centers for Medicare & Medicaid Services perspective. We varied model inputs in one-way and probabilistic sensitivity analyses.

RESULTS

Full Access was less costly and more effective than Current Practice for all cohorts and perspectives, with differences in cost ranging from $5,369 to $11,960 and in effectiveness from 0.82 to 3.01 quality-adjusted life-years. In a probabilistic sensitivity analysis, Full Access was cost saving in 93% of model iterations. Compared with Current Practice, Full Access averted 5,994 hepatocellular carcinoma cases and 121 liver transplants per 100,000 patients.

CONCLUSIONS

Current Medicaid policies restricting hepatitis C treatment to patients with advanced disease are more costly and less effective than unrestricted, full-access strategies. Collaboration between state and federal payers may be needed to realize the full public health impact of recent innovations in hepatitis C treatment.

Ombitasvir, paritaprevir, ritonavir, dasabuvir and ribavirin in cirrhosis after complete destruction of hepatocellular carcinoma

We observed a sustained viral response (SVR) of ombitasvir/paritaprevir/ritonavir, dasabuvir and ribavirin therapy, for 12 wk, in two cases with compensated liver cirrhosis and fully destroyed early hepatocellular carcinoma (HCC). Patients were infected with hepatitis C virus (HCV) genotype 1b and were previous null responders/relapsers to interferon-alpha/ribavirin (IFN/RBV). There was a rapid suppression of HCV RNA to undetectable levels within the first two treatment weeks. SVR was achieved even after marked reduction of the RBV dose. The treatment was well tolerated. Both subjects experienced worsening of liver disease during therapy, in different patterns: severe, transient, predominantly direct hyperbilirubinemia without cytolysis (case 1) or progressive increase of aminotransferases (grade 4) without severe hyperbilirubinemia (case 2). Adverse events spontaneously resolved. The patients remained in a good clinical condition without hepatic decompensation. There was no re-occurrence of HCC. This is the first report for treatment of HCV cirrhosis after complete HCC destruction.

[Real data o viral hepatitis C therapy in the Czech Republic]

We reported the first real data about efficacy of interferon-free therapy of chronic hepatitis C in the Czech Republic. Patients were treated with combined therapy of paritaprevir/ritonavir + ombitasvir + dasabuvir with or without ribavirin. There were 109 patients, predominantly men - 62 (57 %), most of them infected by genotype 1b - 101 patients (93 %), minority infected by genotypes 1a (6/109, 5 %) and 4 (2/109, 2 %). Both treatment-naive (43/109, 39 %), and treatment-experienced patients (66/109, 61 %) were treated. Sustained virological response 12 weeks after therapy termination (SVR12) was 100 %, with exclusion of patients with other reason than virological treatment failure.Key words: dasabuvir - chronic hepatitis C - ombitasvir - paritaprevir/rinonavir - ribavirin.

Management of direct-acting antiviral agent failures

Failure to respond to the approved combinations of multiple direct-acting antiviral agents is relatively low in hepatitis C virus treatment registration studies, with rates of 1% to 7%, depending on the patients' baseline characteristics. In real life, failure is slightly higher, likely because of lower compliance. Treatment failures are usually related to relapse and less often to on-treatment viral breakthrough. Hepatitis C drug-resistant variants are detected in most patients who do not achieve viral eradication. The risk of developing these variants depends on host- and virus-related factors, the properties of the drugs used, and the treatment strategies applied. Patients who carry resistance-associated variants may not obtain benefits from treatment and are at risk of disease progression and transmission of the variants. Whether hepatitis C resistance-associated variants persist depends on their type: NS3-4A variants often disappear gradually after therapy is stopped, whereas NS5A variants tend to persist for more than 2 years. The best way to prevent emergence of resistant variants is to eliminate the virus at the first treatment using highly potent antivirals with genetic barriers to resistance. In patients failing first-generation protease inhibitors, combination therapies with sofosbuvir and NS5 inhibitors have proven effective. Some salvage regimens can be shortened to 12 weeks by addition of ribavirin. The optimal treatment for patients who fail an NS5A inhibitor and those with multidrug-resistant variants remains to be defined, and research efforts should continue to focus on treatment for these patients.

Profile of paritaprevir/ritonavir/ombitasvir plus dasabuvir in the treatment of chronic hepatitis C virus genotype 1 infection

Over the last several years, many advances have been made in the treatment of chronic hepatitis C virus (HCV) infection with the development of direct-acting antivirals. Paritaprevir/ritonavir/ombitasvir with dasabuvir (PrOD) is a novel combination of a nonstructural (NS) 3/4A protein inhibitor boosted by ritonavir, an NS5A protein inhibitor, and an NS5B nonnucleoside polymerase inhibitor. This review aims to discuss the pharmacology, efficacy, safety, drug interactions, and viral drug resistance of PrOD in the treatment of HCV genotype 1 infections. Phase I, II, and III human and animal studies that describe the pharmacology, pharmacokinetics, efficacy, and safety of PrOD for HCV were identified and included. Studies that evaluated patients without cirrhosis (n=2,249) and with cirrhosis (n=422) demonstrated that PrOD for 12 or 24 weeks was effective at achieving sustained virologic response rates (>90%) in patients with genotype 1a or 1b HCV infection. Although indicated for the treatment of HCV genotype 1 infection, PrOD is also recommended for the treatment of HCV in patients coinfected with HIV. Additionally, promising data exist for the use of PrOD in liver-transplant recipients. The most common adverse drug events associated with PrOD included nausea, pruritus, insomnia, diarrhea, asthenia, dry skin, vomiting, and anemia. The high efficacy rates seen coupled with a favorable side effect profile seen with PrOD with or without ribavirin have led to its addition as a recommended treatment regimen for HCV genotype 1 infection.

[Possibilities of IFN-free therapy of hepatitis C]

Chronic hepatitis C therapy using Directly Acting Antivirals (DAA) has high efficacy (till 100 %), minimum contra-indications and extraordinarily favorable safety profile. Primarily, it is necessary to pay attention to drug-drug interactions. However they are well documented and successfully resolvable already in general clinical practice. Current possibilities of interferon-free therapy represent combinations of sofosbuvir with other DAA or with ribavirin and combination of paritaprevir boosted by ritonavir+ombitasvir±dasabuvir (3D combination).

Ombitasvir, paritaprevir co-dosed with ritonavir, dasabuvir, and ribavirin for hepatitis C in patients co-infected with HIV-1: a randomized trial

IMPORTANCE

Patients co-infected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) are at high risk for liver disease progression. However, interferon-based treatments for HCV infection have significant toxicities, limiting treatment uptake.

OBJECTIVE

To assess the all-oral 3 direct-acting antiviral (3D) regimen of ombitasvir, paritaprevir (co-dosed with ritonavir [paritaprevir/r]), dasabuvir, and ribavirin in HCV genotype 1-infected adults with HIV-1 co-infection, including patients with cirrhosis.

DESIGN, SETTING, AND PARTICIPANTS

TURQUOISE-I is a randomized, open-label study. Part 1a of this pilot study was conducted at 17 sites in the United States and Puerto Rico between September 2013 and August 2014 and included 63 patients with HCV genotype 1 and HIV-1 co-infection who were HCV treatment-naive or had history of prior treatment failure with peginterferon plus ribavirin therapy. The study allowed enrollment of patients, including those with cirrhosis, with a CD4+ count of 200/mm3 or greater or CD4+ percentage of 14% or more and plasma HIV-1 RNA suppressed while taking a stable atazanavir- or raltegravir-inclusive antiretroviral regimen.

INTERVENTIONS

Ombitasvir/paritaprevir/r, dasabuvir, and ribavirin for 12 or 24 weeks of treatment as randomized.

MAIN OUTCOMES AND MEASURES

The primary assessment was the proportion of patients with sustained virologic response (HCV RNA <25 IU/mL) at posttreatment week 12 (SVR12).

RESULTS

Among patients receiving 12 or 24 weeks of 3D and ribavirin, SVR12 was achieved by 29 of 31 (94%; 95% CI, 79%-98%) and 29 of 32 patients (91%; 95% CI, 76%-97%), respectively. Of the 5 patients who did not achieve SVR, 1 withdrew consent, 2 had confirmed virologic relapse or breakthrough, and 2 patients had clinical history and phylogenetic evidence consistent with HCV reinfection. The most common treatment-emergent adverse events were fatigue (48%), insomnia (19%), nausea (18%), and headache (16%). Adverse events were generally mild, with none reported as serious or leading to discontinuation. No patient had a confirmed HIV-1 breakthrough of 200 copies/mL or greater during treatment.

CONCLUSIONS AND RELEVANCE

In this open-label, randomized uncontrolled study, treatment with the all-oral, interferon-free 3D-plus-ribavirin regimen resulted in high SVR rates among patients co-infected with HCV genotype 1 and HIV-1 whether treated for 12 or 24 weeks. Further phase 3 studies of this regimen are warranted in patients with co-infection.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01939197.

An interferon-free antiviral regimen for HCV after liver transplantation

BACKGROUND

Hepatitis C virus (HCV) infection is the leading indication for liver transplantation worldwide, and interferon-containing regimens are associated with low response rates owing to treatment-limiting toxic effects in immunosuppressed liver-transplant recipients. We evaluated the interferon-free regimen of the NS5A inhibitor ombitasvir coformulated with the ritonavir-boosted protease inhibitor ABT-450 (ABT-450/r), the nonnucleoside NS5B polymerase inhibitor dasabuvir, and ribavirin in liver-transplant recipients with recurrent HCV genotype 1 infection.

METHODS

We enrolled 34 liver-transplant recipients with no fibrosis or mild fibrosis, who received ombitasvir-ABT-450/r (at a once-daily dose of 25 mg of ombitasvir, 150 mg of ABT-450, and 100 mg of ritonavir), dasabuvir (250 mg twice daily), and ribavirin for 24 weeks. Selection of the initial ribavirin dose and subsequent dose modifications for anemia were at the investigator's discretion. The primary efficacy end point was a sustained virologic response 12 weeks after the end of treatment.

RESULTS

Of the 34 study participants, 33 had a sustained virologic response at post-treatment weeks 12 and 24, for a rate of 97% (95% confidence interval, 85 to 100). The most common adverse events were fatigue, headache, and cough. Five patients (15%) required erythropoietin; no patient required blood transfusion. One patient discontinued the study drugs owing to adverse events after week 18 but had a sustained virologic response. Blood levels of calcineurin inhibitors were monitored, and dosages were modified to maintain therapeutic levels; no episode of graft rejection was observed during the study.

CONCLUSIONS

Treatment with the multitargeted regimen of ombitasvir-ABT-450/r and dasabuvir with ribavirin was associated with a low rate of serious adverse events and a high rate of sustained virologic response among liver-transplant recipients with recurrent HCV genotype 1 infection, a historically difficult-to-treat population. (Funded by AbbVie; CORAL-I ClinicalTrials.gov number, NCT01782495.).

Treatment of HCV with ABT-450/r-ombitasvir and dasabuvir with ribavirin

BACKGROUND

The interferon-free combination of the protease inhibitor ABT-450 with ritonavir (ABT-450/r) and the NS5A inhibitor ombitasvir (also known as ABT-267) plus the nonnucleoside polymerase inhibitor dasabuvir (also known as ABT-333) and ribavirin has shown efficacy against the hepatitis C virus (HCV) in patients with HCV genotype 1 infection. In this phase 3 trial, we evaluated this regimen in previously untreated patients with HCV genotype 1 infection and no cirrhosis.

METHODS

In this multicenter, randomized, double-blind, placebo-controlled trial, we assigned previously untreated patients with HCV genotype 1 infection, in a 3:1 ratio, to an active regimen consisting of a single-tablet coformulation of ABT-450/r-ombitasvir (at a once-daily dose of 150 mg of ABT-450, 100 mg of ritonavir, and 25 mg of ombitasvir), and dasabuvir (250 mg twice daily) with ribavirin (in doses determined according to body weight) (group A) or matching placebos (group B). The patients received the study treatment during a 12-week double-blind period. The primary end point was sustained virologic response at 12 weeks after the end of treatment. The primary analysis compared the response rate in group A with the response rate (78%) in a historical control group of previously untreated patients without cirrhosis who received telaprevir with peginterferon and ribavirin. Adverse events occurring during the double-blind period were compared between group A and group B.

RESULTS

A total of 631 patients received at least one dose of the study drugs. The rate of sustained virologic response in group A was 96.2% (95% confidence interval, 94.5 to 97.9), which was superior to the historical control rate. Virologic failure during treatment and relapse after treatment occurred in 0.2% and 1.5%, respectively, of the patients in group A. The response rates in group A were 95.3% among patients with HCV genotype 1a infection and 98.0% among those with HCV genotype 1b infection. The rate of discontinuation due to adverse events was 0.6% in each study group. Nausea, pruritus, insomnia, diarrhea, and asthenia occurred in significantly more patients in group A than in group B (P<0.05 for all comparisons). Reductions in the hemoglobin level were all of grade 1 or 2; reductions of grade 1 and 2 occurred in 47.5% and 5.8%, respectively, of the patients in group A, whereas grade 1 reductions occurred in 2.5% of the patients in group B.

CONCLUSIONS

In previously untreated patients with HCV genotype 1 infection and no cirrhosis, a 12-week multitargeted regimen of ABT-450/r-ombitasvir and dasabuvir with ribavirin was highly effective and was associated with a low rate of treatment discontinuation. (Funded by AbbVie; SAPPHIRE-I ClinicalTrials.gov number, NCT01716585.).

Retreatment of HCV with ABT-450/r-ombitasvir and dasabuvir with ribavirin

BACKGROUND

In this phase 3 trial we evaluated the efficacy and safety of the interferon-free combination of ABT-450 with ritonavir (ABT-450/r), ombitasvir (also known as ABT-267), dasabuvir (also known as ABT-333), and ribavirin for the retreatment of HCV in patients who were previously treated with peginterferon-ribavirin.

METHODS

We enrolled patients with HCV genotype 1 infection and no cirrhosis who had previously been treated with peginterferon-ribavirin and had a relapse, a partial response, or a null response. Patients were randomly assigned in a 3:1 ratio to receive coformulated ABT-450/r-ombitasvir (at a once-daily dose of 150 mg of ABT-450, 100 mg of ritonavir, and 25 mg of ombitasvir) and dasabuvir (250 mg twice daily) with ribavirin (1000 or 1200 mg daily) or matching placebos during the 12-week double-blind period. The primary end point was the rate of sustained virologic response 12 weeks after the end of study treatment. The primary efficacy analysis compared this rate among patients assigned to the active regimen with a historical response rate (65%) among previously treated patients with HCV genotype 1 infection and no cirrhosis who had received retreatment with telaprevir and peginterferon-ribavirin.

RESULTS

A total of 394 patients received at least one study-drug dose. In the active-regimen group, 286 of 297 patients had a sustained virologic response at post-treatment week 12, for an overall rate of 96.3% (95% confidence interval, 94.2 to 98.4). This rate was noninferior and superior to the historical control rate. Rates were 95.3% among patients with a prior relapse (82 of 86 patients), 100% among patients with a prior partial response (65 of 65 patients), and 95.2% among patients with a prior null response (139 of 146 patients). Pruritus occurred more frequently with the active regimen (in 13.8% of patients) than with placebo (5.2%, P=0.03). Three patients in the active-regimen group (1.0%) discontinued the study drugs owing to adverse events. Hemoglobin values of grade 2 (8.0 to <10.0 g per deciliter) and grade 3 (6.5 to <8.0 g per deciliter) occurred in 4.7% and 0.3% of patients in the active-regimen group, respectively.

CONCLUSIONS

Rates of response to a 12-week interferon-free combination regimen were more than 95% among previously treated patients with HCV genotype 1 infection, including patients with a prior null response. (Funded by AbbVie; SAPPHIRE-II ClinicalTrials.gov number, NCT01715415.).

Bladder cancer screening program for a petrochemical cohort with potential exposure to beta-napthylamine

Approximately 1800 workers in pipe manufacturing plants in the United States may have been exposed to beta-napthlyamnine between 1970 and 1996. Once the chemical was detected, the contaminated additive in the resin was identified and discontinued. A bladder cancer-screening program was initiated in 1999. An annual two-stage screening program was developed to test for microscopic hematuria (stage one) and cytology (stage two), with a urology referral of positive or suspicious cytology. This paper presents the program methodology, cohort enumeration, recruitment, and enrollment strategies, and screening protocol. Enrollment data from the first 3 years are presented. Annual screening of a cohort of current and former employees is feasible. Original personnel records are often incomplete, making cohort identification important. Personal contact and follow-up are key elements of successful recruitment and retention.

Improvement in the histochemical localization of leucine aminopeptidase with a new substrate, L-leucyl-4-methoxy-2-naphthylamide

A new method for the histochemical demonstration of leucine aminopeptidase in fresh frozen sections was developed with the substrate L-leucyl-4-methoxy-2-naphthylamide. The superior enzyme localization is due to the more rapid rate of coupling of the hydrolysis product, 4-methoxy-2-naphthylamine as compared to 2-naphthylamine itself, and to the low lipid solubility and high substantivity for protein of the copper chelate of the dye formed on coupling with tetrazotized diorthoanisidine. A comparison of the old and the new method is illustrated, and a description is given of the localization of leucine aminopeptidase in the tissues of the rat and man.